Coil core manufactured from softmagnetic and permanent-magnetic materials



Oct. 29, 1968 WULLKOPF ETAL 3,408,573

H. COIL CORE MANUFACTURED FROM SOFT-MAGNETIC AN PERMANENT-MAGNETIC MATERIALS Filed June 8, 1966 /i F i 4 Fl .3 g g INVENTORS HELLMUTH WULLKOPF GERD SAMOW BY W lidt;

AGENT United States Patent 3,408,573 COIL CORE MANUFACTURED FROM SOFT- MAGNEIIC AND PERMANENT-MAGNETIC MATERIALS Hellmuth Wullkopf, Harksheide, and Gerd Samow, Hamburg Fuhlsbuttel, Germany, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed June 8, 1966, Ser. No. 556,144 Claims priority, application Germany, June 19, 1965, P 37,088 7 Claims. (Cl. 335-297) The invention relates to a coil core manufactured from soft-magnetic and permanent-magnetic materials in which the permanent magnetic material serves for bias magnetization of the soft-magnetic material.

A coil core is already known which consists of several layers of ferrite material in which the material of one of the layers has permanent magnetic properties so that therewith the remaining (soft-magnetic) part of the coil core can be biased. However, the manufacture of sintered cores built up from layers of different materials meets serious objections due to the different coefficients of thermal exicated shapes of the core cannot be manufactured or are difiicult to manufacture according to this known method.

In the coil core according to the invention the abovementioned drawbacks are avoided. In fact, said core consists of a mixture of soft-magnetic and permanent-magnetic materials in powder form homogeneously distributed in a solid binder, preferably rubber or a synthetic material.

For the manufacture of the coil cores according to the invention soft-magnetic and permanent-magnetic materials in powder form are thoroughly mixed together with a are then formed into a body by moulding, injection moulding or rolling, the binder being then hardened. In this manner it is possible to manufacture coil cores of a complicated shape in a simple manner.

The coil cores are preferably constructed as solid coil formers. According to another embodiment of the invention, the coil cores are constructed as bodies moulded or injection-moulded close around the coil Winding.

As a result of the homogeneous mixing of the softmagnetic and the permanent-magnetic materials, the softmagnetic material can be better subjected to bias magnetisation than is the case in the known coil cores built up from layers of soft-magnetic and permanent-magnetic material.

When in manufacturing a coil core according to the invention a DC. magnetic field is applied while the permanent magnetic particles can move freely to a certain extent with respect to one another so that the permanentmagnetic particles are directed parallel to said D.C. magnetic field with their easy axis of magnetisation, the particles of the permanent-magnetic material'in the core after solidification of the binder are fixed in a magnetically oriented condition.

As soft-magnetic and permanent-magnetic materials are preferably chosen ferrites, for example, soft-magnetic manganese-zinc ferrite or nickel-zinc ferrite and permanent-magnetic bariumhexaferrite and/or strontiumhexaferrite respectively. Other soft-magnetic material may also be used, such as, carbonyl iron or iron powder. As permanent-magnetic materials are further to be considered the known permanent-magnetic steel alloys or manganesebismuth alloys.

The quantity of soft-magnetic material in the coil cores according to the invention preferably is at least 50% by weight, in particular approximately 70-80% by weight, of the total quantity of ferromagnetic material present in 3,408,573 Patented Oct. 29, 1968 It is to be noted that flexible bodies consisting of either only a softmagnetic material or only a permanent-magup from a permanent-magnetic and a soft-magnetic layer each consisting of a magnetic powder with a binder. In

the invention relates to a ferro-magnetic coil core having a high magnetic permeability and an operating point which, by

there.

In order that the invention may readily be carried into effect, a few examples will now be described in greater detail with reference to the drawing, in which:

longitudinal cross-sectional view of a saturation is reached plan view of the coil construction shown soft-magnetic and permanent-magnetic material, preferably ferrites, and a solid binder, for example, a thermoplastic or thermo-hardening resin. The powdered starting material has been given the shape of the coil core 1 as shown by moulding.

The permanent-magnetic material, for example, barium-hexaferrite, produces a bias magnetisation of the soft magnetic material (which consists, for example, of manganese-zinc ferrite). This coil construction consequently control for television receivers and is distinguished from the known linearity controls by its simplicity; in fact it consists of only two parts, the coil core 1 and the winding 2. If required, to increase the adjusting range of the linearity control shown in FIGURE 1, another soft-magnetic core 4, preferably likewise consisting of manganese-zinc ferrite, is movably arranged in the cavity 5 of the coil core 1.

In the coil construction shown in FIGURES 3 and 4, an annular coil winding 6 was hardened. the connection body.

What is claimed is:

1. A coil core manufactured from soft-magnetic and permanent-magnetic materials in which the permanentmembers 9 projecting beyond the core magnetic material serves for bias magnetization of the soft-magnetic material, characterized in that the coil core consists of a mixture of soft-magnetic and permanentmagnetic materials in powder form homogeneously distributed in a solid plastic binder.

2. A coil core as claimed in claim 1, characterized in that the particles of the permanent-magnetic material present therein are magnetically oriented.

3. A coil core as claimed in claim 2, characterized in that the quantity of soft-magnetic material present therein is at least 50% by weight of the total quantity of ferromagnetic material in the core. I

4. A coil core as claimed in claim 3, characterized in that the weight ratio of the total quantity of ferromagnetic material and the quantity of binder lies approximately between 4:1 and 9:1.

5. A coil core as claimed in claim 4, characterized in that said core is constructed as a solid coil former.

6. A coil core as claimed in claim 5, characterized in that the said core is constructed as a body moulded close around a coil winding.

7. A coil core as claimed in claim 6, characterized in that the soft-magnetic and permanent-magnetic materials are ferrites.

References Cited UNITED STATES PATENTS 2,452,531 10/1948 Snoek 335-297 XR GEORGE HARRIS, Primal Examiner. 

1. A COIL CORE MANUFACTURED FROM SOFT-MAGNETIC AND PERMANENT-MAGNETIC MATERIALS IN WHICH THE PERMANENTMAGNETIC MATERIAL SERVES FOR BIAS MAGNETIZATION OF THE SOFT-MAGNETIC MATERIAL, CHARACTERIZED IN THAT THE COIL CORE CONSISTS OF A MIXTURE OF SOFT-MAGNETIC AND PERMANENTMAGNETIC MATERIALS IN POWDER FORM HOMOGENEOUSLY DISTRIBUTED IN A SOLID PLASTIC BINDER. 